1. Field of the Invention
This invention relates to apparatus for treating horizontal structure surfaces, and more particularly, to an air sweep system for a mobile surface abrading apparatus which utilizes air circulation to recycle rebounding abrasive from the treated surface through a concentric dual rotating screen separation system and into a hopper, where it is fed to an abrasive propulsion device or devices, and where the abrasive media or particles are projected at the treated surface at high velocity in angular relationship. The rebounding abrasive particles and surface materials such as dust, aggregate and debris, are recovered from the treated surface by air flow through one or more vertical abrasive conveyors. The mobile surface abrading apparatus is capable of operating with one or more mechanical air-operated conveyance devices providing energy to the abrasive particles for transporting the abrasive particles and surface debris to the separation system.
This invention is characterized by a continuous air flow system and an improvement in the lifting of abrasive, aggregate and debris in a vertical or near-vertical direction with air movement alone, allowing one or more propulsion devices to treat a surface area adjacent to the air flow conveyor. The principle involves a selected air flow which is forced through restricted passages or channels, where particulate transfer is effected and non-restricted areas where separation of air and abrasive particles is accomplished. The abrading apparatus includes passages that allow abrasive and other particulate to be received from one or more angles, which facilitates an internal area of sufficient size to sustain an appropriate air velocity which forces the various particles to be encountered, both transversely in the sweeping function and upwardly in the conveying function, against the pull of gravity.
In the vertical conveying function, the maximum speed at which any object will fall is reached when atmospheric friction equals gravitational pull, and this speed is known as the terminal velocity. The air flow system of this invention is designed to slightly exceed this terminal velocity and thus convey the abrasive particles upwardly through the apparatus. The pneumatic conveyance of abrasive particles in the apparatus of this invention would not normally require dust-handing equipment. Nonetheless, the abrading operation is very dusty unless a dust collector is used and dust collection is mandated by environmental laws and common sense. Accordingly, a blower must be used to exhaust the cleaned air from the dust collector. This invention combines a dual purpose pressure blower that is properly sized for the volume and intensity necessary to satisfy the needs of the dust filters and the vertical abrasive and debris conveying chamber to recycle the spent abrasive particles.
Sweeping of the horizontal structure surface to be treated is accomplished by allowing air that usually leaks around surface seals to enter the blast area, normally from the trailing wall of the apparatus, in such a way that the abrasive particles do not escape. There is a constant spatter of abrasive particles at the point where the blast stream of abrasive particles strikes and deflects from the structure surface. An abrasive particle collision on or about the surface level at a sharp angle can cause the abrasive particles to project forcefully and abruptly in different directions. If an opening is located in the apparatus where abrasive particles can project, by deflection or directly, to the outside, these misdirected abrasive particles will escape at high speed, causing damage to machinery and constituting a danger to personnel in the immediate area. The apparatus of this invention facilitates entry of air, at least at the trailing wall of the blast head, after being forced at high speed across a given structure surface area, without the danger presented by escaping particulate. Upon entry into the apparatus, air velocity sweeps through the machine and only a small percentage of abrasive particles becomes wedged in crevices where the blast head contacts the treated surface.
The improvement of this invention includes carefully forming a passageway or corridor in which the lower containment structure constitutes the treated structure surface area behind the blasting area and an upper wall that is adjustable in order to vary the internal air intake area, and therefore the velocity, of the upwardly deflected abrasive particles at a selected air flow. A pair of spaced floating deflector seals contact and seal at the structure surface. A third side or wall is supplied with fixed resilient seal and a fourth, or trailing wall is open to the atmosphere for the intake of air. This corridor defines a passageway in which air is forced, either longitudinally or transversely, but in either case horizontally, across the structure surface immediately behind the blast travel area, in order to entrain loose abrasive and debris particles. This horizontal air flow has adequate force at structure surface level to entrain any loose particles lying there and convey the abrasive and debris particles through a labyrinth-type passageway or corridor. The corridor is constructed in such a way as to make it virtually impossible for any of the particles to escape the blast area under the force of retained kinetic energy.
Another improvement includes at least one drum journalled for rotation with respect to the carrying vehicle and tilted with respect to the horizontal, a fine screen defining the outside cylindrical surface of the drum, a coarse screen defining an inside cylindrical surface of the drums in spaced, concentric relationship with respect to the fine screen, a screen broom located in contact with the fine screen for cleaning purposes, and at least one paddle or blade and cone mounted in the drum at a transverse drum wall having an opening at the central axis. The drum receives abrasive particles, particulate aggregate and dust which rebound from the treated surface and are entrained in the incoming air stream and separates these components.
2. Description of the Prior Art
In existing surface treating machines utilizing an abrasive propulsion device, the abrasive is hurled toward the surface to be treated and after striking the structure surface, the abrasive deflects at an angle. In smaller machinery, the rebounding kinetic energy is usually sufficient to transfer the abrasive particles to a point above the abrasive propulsion device, therefore completing a cleaning cycle with no further (or very little) input of energy necessary to recycle the abrasive particles.
A problem exists when this technique is operated on soft or irregular surfaces where most of the kinetic energy in such an operation is absorbed or misdirected, since there is insufficient abrasive rebound to complete the recovery and redirection cycle. Another problem exists when the machine is sufficiently large to require that the rebounding abrasive particles reach a higher level than would normally be necessary in smaller machines. There is only a finite quantity of kinetic energy storage possible in an abrasive particle and this energy varies according to the size of the abrasive particle and the angle at which it strikes the structure surface. The larger the particle and the less the angle at which it strikes the structure surface, the higher the level of kinetic energy retained.
When an abrasive is used that is sufficiently small to provide good cleaning area coverage and when this abrasive is propelled toward the horizontal structure surface at any angle that would facilitate a productive amount of work, there is usually not an adequate amount of energy left in the abrasive particle to reach a very high level in the recovery mechanism. In the past, machines which needed a higher elevation of spent abrasive particles relied on magnets, rotary brooms, bucket elevators and the like, to lift particles beyond the rebound energy boundary.
There are various devices known in the art for abrading road and other horizontal structure surfaces for the purpose of texturing and cleaning the surfaces. In each case, the accepted technique includes forcing the abrasive particles at the structure surface to be textured or cleaned in angular relationship and utilizing various techniques, including abrasive rebound energy, to recycle the particles back to the abrasive propulsion device or devices. In addition to the rebounding energy mechanism, other techniques such as magnets, rotary brooms, mechanical conveyors and elevators, as well as induced air currents with entry points at or above structure surface levels, have been used with varying degrees of success, to recover and recycle the abrasive particles. One problem which has become apparent regarding machines which depend mostly on rebound for abrasive recycling, is the lost kinetic energy of the abrasive particles after they strike the structure surface to be abraded. This energy loss causes the particles to drop back onto the structure surface, where they accumulate and are lost from the recycle process. If this condition becomes sufficiently pronounced to form a multiple layer of abrasive on the surface to be abraded, additional abrasive propelled onto this accumulated layer will lose virtually all kinetic energy upon contact with the layer due to absorption, thereby compounding the rebounding problem. Under these conditions, total evacuation of the abrasive supply hopper in the machine soon occurs and the accumulation of abrasive particles must then be recovered from the structure surface, usually by manual labor, using brooms, shovels and buckets to reload the hopper, thus necessitating costly machine downtime.
In my U.S. Pat. No. 4,433,511, dated Feb. 28, 1984, entitled "Mobile Abrasive Blasting Surface Treating Apparatus", I detail a mobile apparatus for treating structure surfaces by abrasive blasting. The apparatus includes a mobile housing with self-propelled, endless tracks for traversing the surface to be treated. The housing includes a reservoir for containing abrasive particles and a rotary wheel with blades that rotate to propel the abrasive particles against the surface to be treated in angular relationship and abrade or etch the surface. A return passage for the particles has an opening at the angle of rebound of the particles extending toward the reservoir and multiple trays receive the recirculating particles and fill with particulate material, which material then spills into the reservoir. Particulate material on the trays absorbs the kinetic energy from the following or trailing particles to prevent further rebounding. The particles spill from the trays in a stream or sheet, intersected by a stream of air and trays separate the more coarse particulate debris from the abrasive particles en route back to the reservoir. Dust collectors are provided to separate the dust from the air used in separating coarse debris from the abrasive particles and from the air flow, to assist in sweeping debris from beneath the apparatus.
Typical of the abrading devices known in the prior art are those detailed in the following U.S. Pat. No. 1,954,111, dated Apr. 10, 1934, to J. Wilkes, entitled "Machine for Abrading Concrete Surfaces"; U.S. Pat. No. 3,858,359, dated Jan. 7, 1975, to Raymond M. Leiliart, entitled "Mobile Surface Treating Apparatus"; U.S. Pat. No. 3,877,175, dated Apr. 15, 1975, to Clyde A. Snyder, entitled "Mobile Surface Treating Apparatus"; U.S. Pat. No. 3,906,673, dated Sep. 23, 1975, to T. Goto, et al, entitled "Abrasive Cleaning Machine"; U.S. Pat. No. 3,934,373, dated Jan. 27, 1976, to Raymond M. Leiliart, entitled "Portable Surface Treating Apparatus"; U.S. Pat. No. 3,977,128, dated Aug. 31, 1976, to James R. Goff, entitled "Surface Treating Apparatus"; U.S. Pat. No. 4,080,760, dated Mar. 28, 1978, to Raymond Leiliart, entitled "Surface Treatment Device Including
Magnetic Shot Separator"; U.S. Pat. No. 4,052,820, dated Oct. 11, 1977, to John C. Bergh, entitled "Portable Surface Treating Apparatus"; U.S. Pat. No. 4,336,671, dated Jun. 29, 1982, to Robert T. Nelson, entitled "Surface Cleaning Apparatus"; U.S. Pat. No. 4,364,823, dated Dec. 21, 1982, entitled "Apparatus for Separating Abrasive Blasting Media from Debris"; U.S. Pat. No. 4,376,358, dated Mar. 15, 1983, to John J. Shelton, entitled "Surface Treating Apparatus"; U.S. Pat. No. 4,377,922, dated Mar. 29, 1983, to John C. Bergh, entitled "Portable Apparatus for Treating Surfaces"; U.S. Pat. No. 4,377,923, dated Mar. 29, 1983, to John C. Bergh, entitled "Surface Treating Apparatus"; U.S. Pat. No. 4,377,924, dated Mar. 29, 1983, to John C. Bergh, entitled "Portable Device for Treating Surfaces"; U.S. Pat. No. 4,382,352, dated May 10, 1983, to Robert T. Nelson, entitled "Apparatus for Cleaning Surfaces, Including Means for Separating Debris and Abrasive Material"; U.S. Pat. No. 4,394,256, dated Jul. 19, 1983, to James R. Goff, entitled "Apparatus for Separating Abrasive Blasting Media from Debris"; U.S. Pat. No. 4,406,092, dated Sep. 27, 1983, entitled "Surface Cleaning Machine"; U.S. Pat. No. 4,416,092, dated Nov. 22, 1983, entitled "Cleaning Apparatus"; U.S. Pat. No. 4,646,481, dated Mar. 3, 1987, to Wayne E. Dickson, entitled "Surface Blasting Apparatus"; and U.S. Pat. No. 4,693,041, dated Sep. 15, 1987, to Wayne E. Dickson, entitled "Surface Blasting Appartus".
It is an object of this invention to provide a new and improved controlled velocity air sweep system for sweeping abrasive, road debris and dust through a rotating drum separation system and circulating the abrasive back to one or more abrasive propulsion devices with minimum loss of abrasive.
Another object of the invention is to provide a velocity-adjustable air sweep system for a mobile road surface texturing apparatus, which system does not depend upon the rebound energy of the abrasive for separation and recirculation to the abrasive propulsion device or devices.
Yet another object of the invention is to provide an air sweep system for sweeping a treated surface of abrasive particles and road debris such as aggregate and dust and transferring the abrasive particles, road debris and dust to a new and improved rotating drum separation system for separation, where the abrasive particles are recycled for feeding to the abrasive propulsion device or devices.